In recent years, imaging apparatuses using optical coherence tomography (OCT) that utilizes interference of low coherent light (hereinafter also referred to as OCT apparatuses) have been put into practical use. Since an OCT apparatus can acquire a tomographic image only with a resolution substantially equivalent to the wavelength of light incident on an object to be examined, a tomographic image of a sample can be obtained with a high resolution. Particularly in the ophthalmologic field, the OCT apparatus is useful for obtaining a tomographic image of a retina at the eyeground.
A composite apparatus using an OCT apparatus and a retinal camera (an apparatus for capturing a surface image or a two-dimensional image of the eyeground) in combination is also useful. As such a composite apparatus, Japanese Patent Laid-Open No. 2007-252693 discloses an apparatus capable of simultaneously capturing a surface image and a tomographic image of the eyeground. In this composite apparatus, an OCT apparatus is connected to an optical connector of a retinal camera. When a control button of a joystick provided in the retinal camera is pressed, a surface image and a tomographic image of the eyeground are captured simultaneously.
The time taken to capture multiple tomographic images with the OCT apparatus is longer than the time taken to capture surface images of the eyeground with the retinal camera, and often becomes about several seconds. When a tomographic image is captured with the OCT apparatus, the brightness of an acquired tomographic image is low or the positions of a plurality of tomographic images are misaligned because of a blink or involuntary eye movement (the eye of a subject to be examined randomly and slightly moves against the subject's intention not to move the eye) of the subject. As a result, a desired area that is important in diagnosing the retina and optic disk of the eyeground may not be included in the acquired image. In this case, there is a need to capture a tomographic image of the eyeground of the subject again.
In the apparatus disclosed in Japanese Patent Laid-Open No. 2007-252693, when the control button of the joystick provided in the retinal camera is pressed, a tomographic image is first captured, and a surface image of the eyeground is subsequently captured. Thus, a tomographic image and a surface image are captured in succession in this order by one press of the control button. In this case, the surface image of the eyeground is captured before the operator checks the tomographic image.
In contrast, to obtain an image of the eyeground with the retinal camera, it is necessary to illuminate the eyeground with a flare of flashlight. Since the quantity of illumination light is large, the pupil of the subject contracts after a surface image of the eyeground is captured. In this case, according to the subject, it takes several minutes until the pupil dilates. For this reason, the next tomographic image can be captured only when several minutes pass after the surface image of the eyeground is captured.
For the above-described reason, the user of the apparatus needs to wait for a long period to capture a tomographic image again after a surface image of the eyeground is captured, and this reduces usability. Moreover, the subject whose eyeground is to be imaged has a heavy time load.